I beams comprise two parallel flanges and a central web extending between them. In a typical method of making steel I beams, the flange line drives the making of webs. That is, the flanges for several jobs are all made out of the same thickness of bar stock material, and stacked in the intended order of use at a tack welding station. A group of flanges may be made from one size of bar stock. These flanges are numbered in the order they are produced, pairs of flanges, inside and outside, being made for each beam. If another size of bar stock is then needed the flange numbers continue sequentially with flanges of that next pair. The webs that match these flanges are then produced at a web cutting station. The webs are made at the web cutting station in a manner that results in efficient utilization of the web stock Therefore, the webs may be nested together so as to include webs out of the sequence dictated by the flanges. When the webs are sorted and stacked in the same sequential order as the flanges, any webs out of sequence would be placed aside until its place in the sequence arises. The stacks of webs are numbered in a sequence that corresponds to the sequence of the stacked flanges.
Plates of web stock of a predetermined length are loaded by crane onto a water table at a cutting station. The cutting station may employ a plasma torch utilizing nitrogen cutting gas. The machine cuts a nest of webs out of individual plates of web stock which are available in different lengths. A computer “nesting” program determines the most efficient manner in which to cut webs of the desired size from the plate. At the cutting station there is a significant amount of scrap material that cannot be used to make the desired webs. The way the nesting software organizes the webs efficiently for cutting from individual plates results in waste known as “drop,” which can be end drop or side drop depending on the location where it is generated. When the cutting is complete, a crane is used to remove the waste material, and the webs are sorted and stacked. The webs are stacked in a desired order of use, which matches the order of the flanges that have been made i.e., the web to be used first is on top of the stack, the next web to be used is disposed beneath it and so on. After the webs and scrap are removed from the cutting machine, the next plate of web stock is loaded into place and webs are cut from it in the same manner.
A stack of the webs is then moved near a conveyor at a seam welding station. Oftentimes, webs must have a length that is longer than the web stock. Such webs are made by seaming webs together end-to-end at the seam station. Otherwise, if no seam is required the webs are moved in the order in which they are stacked onto the conveyor near the seam station and pass by the seam station. The single and multipiece webs are conveyed past the seam station to a tack station where they are mated with the appropriate flanges in the order in which the flanges made at the flange station are stacked, and then two flanges are tack welded on either side of each web. The tack welded web and flanges are then conveyed to a beam welding station which welds the flanges to the web to form a beam. After the beam is formed it is removed from the exit conveyor after the beam welding station and matching detail parts are placed on it. The beam is transported by crane to a finish welding station where the detail parts are hand welded to the beam.
The conventional process is inefficient and wasteful. Workers are continuously using cranes to stack and unstack material and to transport and store the stacks. For example, the web portions which are cut from the web stock are sorted and stacked and then moved by crane to a seaming station to be welded together to form webs of longer length. The flanges are made and then sorted and stacked and moved by crane to the tack welding station.
Working with stacks requires equipment including lifting devices, chains, slings, and spreader bars, as well as storage space and crane operators. All of this stacking, unstacking, restacking and moving of stacks is undesirable because, although it is necessary for the conventional process, it adds nothing of value to the final beam. Despite the inefficiency of stacking, unstacking, moving and storing stacks of material, and the wastefulness and inefficiency of current methods of cutting webs and welding web portions together to make multi-piece webs, this process of making beams has been used in the industry for many years.
A disadvantage of this process is that many of the jobs ordered by builders are mixed together at one time. A builder may want a job placed at a high priority. However, that particular job is intermingled with other jobs and cannot be produced any quicker without extreme difficulty. Conversely, if production begins and then a builder contacts the beam manufacturer and indicates that he will not need the beams of his job completed soon, it is very difficult if at all possible to pull his low priority job from the fabrication cycle. As a result, the low priority job slows down the production of higher priority jobs.
The present invention enables webs to be made with good plate utilization, avoids making stacks and enables production to be more responsive to builders job priorities.